1. Field of the Invention
This invention relates broadly to a fluid flow control valve mechanism and more specifically to a valve mechanism for controlling the vacuum signal to a spark advance mechanism.
2. Prior Art
In order to control the quantity of fluid flow between inlet and outlet ports, conventional valve mechanisms include a valve member of the needle type which variably controls the fluid communication between the inlet and outlet ports in proportion to a control signal. Such a needle valve member has a valve surface which is adapted to be spaced from a valve seat so that the quantity of fluid flow is controlled in proportion to the spacing between the needle valve and seat.
In prior mechanisms, however, it is quite difficult to accurately set the spacing to control a very small quantity of fluid flow. Small particles of foreign matter can readily prevent the accurate spacing control of the needle valve.